A Lab Assembled Microcontroller-Based Sensor Module for Continuous Oxygen Measurement in Portable Hypoxia Chambers

Abstract

BackgroundHypoxia-based cell culture experiments are routine and essential components of in vitro cancer research. Most laboratories use low-cost portable modular chambers to achieve hypoxic conditions for cell cultures, where the sealed chambers are purged with a gas mixture of preset O2 concentration. Studies are conducted under the assumption that hypoxia remains unaltered throughout the 48 to 72 hour duration of such experiments. Since these chambers lack any sensor or detection system to monitor gas-phase O2, the cell-based data tend to be non-uniform due to the ad hoc nature of the experimental setup.MethodologyWith the availability of low-cost open-source microcontroller-based electronic project kits, it is now possible for researchers to program these with easy-to-use software, link them to sensors, and place them in basic scientific apparatus to monitor and record experimental parameters. We report here the design and construction of a small-footprint kit for continuous measurement and recording of O2 concentration in modular hypoxia chambers. The low-cost assembly (US$135) consists of an Arduino-based microcontroller, data-logging freeware, and a factory pre-calibrated miniature O2 sensor. A small, intuitive software program was written by the authors to control the data input and output. The basic nature of the kit will enable any student in biology with minimal experience in hobby-electronics to assemble the system and edit the program parameters to suit individual experimental conditions.Results/ConclusionsWe show the kit’s utility and stability of data output via a series of hypoxia experiments. The studies also demonstrated the critical need to monitor and adjust gas-phase O2 concentration during hypoxia-based experiments to prevent experimental errors or failure due to partial loss of hypoxia. Thus, incorporating the sensor-microcontroller module to a portable hypoxia chamber provides a researcher a capability that was previously available only to labs with access to sophisticated (and expensive) cell culture incubators.

pH, Lactate, and Hypoxia: Reciprocity in Regulating High-Affinity Monocarboxylate Transporter Expression in Glioblastoma

“…Eight to 12 hours posttransfection, media in the 24-well plates were replaced with 1.0 ml Optimem-I containing 4% FBS (same medium used to plate cells). The plates were placed in a modular hypoxia chamber (MIC-101; Billups-Rothenberg, Inc., Del Mar, CA) equipped with a lab-assembled O 2 monitor [36] and a flow meter (SFM3001; 3-25 LPM adjustable flow rate; Billups-Rothenberg). The chamber was purged with a 5% CO 2 , 95% N 2 gas mixture until the chamber O 2 level dropped to 0.5%.…”

“…The chamber was placed in a 37°C incubator and repurged 1 hour later to readjust gas-phase O 2 down to 0.5%. Note: This second step is critical for long-term maintenance of hypoxia between 0.5% and 1.0% [36]. Chamber O 2 % was monitored (maintained below 1%) for the next 48 hours, the plates were removed, and luminescence of the cells was assayed as described before.…”

An Inexpensive Incubator for Mammalian Cell Culture Capable of Regulating O2, CO2, and Temperature

“…It is capable of maintaining pre-set O 2 , CO 2 and temperature values within the physiological ranges for most mammalian cells. Although other "lab-assembled" O 2 monitoring systems [11], imaging systems [12], and cell culture incubators [13,14] exist, we are unaware of any that simultaneously regulate O 2 and CO 2 to enable experiments to be conducted at physiological O 2 levels. Thus, our incubator represents the least expensive solution to the important issue of maintaining physioxia in cell culture that is currently available.…”

Transportable system enabling multiple irradiation studies under simultaneous hypoxia in vitro

“…In addition to commercially available products, there are also other solutions including a hypoxic atmosphere generated in a plastic bag [ 28 ] or in a self-made hypoxia containers [ 29 ]. Although budget-friendly, the oxygen conditions inside these types of hypoxia containers is difficult to maintain without feedback control [ 30 ]. Furthermore, the final oxygen level in the culture medium depends on the materials placed inside the chamber [ 21 , 31 ].…”